Our long-term objective has been to elucidate the necrosis factor (TNF) represses the acetyl-CoA carboxylase (ACC) gene. ACC is the enzyme that carries out the rate-limiting reaction in the biogenesis of long chain fatty acids. Treatment of whole animals or cancer patient with TNF causes, in addition to tumor necrosis, a number of pathophysiological conditions. These include inhibition of lipid synthesis, depletion of lipid reserves, hypotension, and anorexia. Our hypothesis has been that the complex effects of TNF in whole animals and humans may be due to a common mechanism by which TNF acts on the promoters of several different genes. During the tenure of the initial grant period, we identified the DNA sequences in the promoter of the ACC gene which are required for TNF repression of the gene. Furthermore, a nuclear factor whose binding to the TNF specific sequences has been demonstrated to decrease upon TNF treatment of 3OA5 preadipocytes. In these studies, we will continue to use 3OA5 preadipocytes to demonstrate that the binding of the nuclear factor to the TNF specific DNA sequence is causally related to the repression of the ACC gene. In addition, experimental plans to demonstrate that: a) the nuclear protein is a tyrosine phosphoprotein, and b) TNF regulation of the binding activity of the nuclear factor is due to its regulation of protein tyrosine phosphatase in the nucleus. This approach should help us understand how lipid biogenesis affects the growth and maintenance of cancer cells and how TNF affects lipid biogenesis leading to cachexia, a condition universally observed in cancer patients. I hope that knowledge gained from the proposed studies will help us better understand eukaryotic gene expression at the level of specific gene repression mechanisms. Our studies should also help us understand how the biosynthesis of fatty acids and lipids is regulated at the gene level and they may eventually provide insights into the complex medical problems associated with obesity.